A807 Studer heads question

[TIMTAPE]

Peter (Reelguy) or Ted may know the answer to this one.

I'm working on an A807. I've not worked on one before. The record and play heads were grooved and so I relapped them. They're fine now and the machine is coming up to spec nicely, but I was suprised that the heads had no relief slots milled in them. In fact relapping them was necessary because of the absence of relief slots and the resultant grooved heads with the consequent trapping of oxide in the corners. If there had been relief slots I might have got away without relapping.

Was it normal for the A807 heads to have no slots or is it possible the heads have been already relapped so heavily that the original relief slots have been ground away?

Cheers Tim

[ricard]

Not really knowing the answer, but weren't relief slots generally fairly deep so that relapping down to the bottom of the slot would have have at least caused the gap to open if not destroying the head?

Also your post is the first time I've heard anyone mention oxide getting trapped 'in the corners' of the head groove, which is a phenomenon I must have heard the symptoms of umpteen times on older machines with worn heads. It's been a private theory of mine but I've never had it confirmed before.

[TIMTAPE]

Hi Ricard,

Re depth of the slots I'm not sure either. I know Revox B77/PR99 heads can wear right down to the bottom of the slot and still have not worn right through. I guess it depends on how deeply they cut the slot on a particular head.

Re "dirt trapped in the corner" it's certainly hard to remove it by normal cleaning methods. I'm sure it helps to explain why on a quarter track machine, track 1-4 at the edge of the tape tends to fare worse than track 3-2.

Cheers Tim

[Amraduk]

Hello Tim,

Originally Posted by TIMTAPE

I know Revox B77/PR99 heads can wear right down to the bottom of the slot and still have not worn right through.

Surely, the B77 heads don't have relief slots? The B77 I have certainly doesn't!

Regards,

Dave.

[TIMTAPE]

Worth a thousand words...

[Amraduk]

Hello Tim,

Originally Posted by TIMTAPE

Worth a thousand words...

The heads on my B77 MKI do not have those slots!

Regards,

Dave.

[TIMTAPE]

Dave,

They must have been relapped down to the bottom of the slots. Do you have a photo?

Regards,

Tim

[Amraduk]

Hello Tim,

Originally Posted by TIMTAPE

They must have been relapped down to the bottom of the slots.

Not that I'm aware of, though it is a possibility.

Do you have a photo?

Not at the moment. I'll try and take one later.

Regards,

Dave.

[Ted Kendall]

I have never seen a modern pattern Revox or Studer head without guttering. If yours hasn't got it, it has already been ground to glory.

[reelguy]

Sorry Tim, I have never managed to get hold of an A807 Studer .Nor any other Studer model.Only Revox A77s.
But looking at the pic of that head it does look as if it has had a hard life.
Hope you manage to sort it out.

I was under the impression that heads from the A77 Revox could be used on other Studer ?Revox Mcs but I am not really sure.

Regards Peter W....Reelguy

[Amraduk]

I have taken a much closer look at the heads on my B77 and it appears that they do have relief slots but they are quite shallow and not easy to see. I have attached a photo, it's not very good but it is the best I can achieve with my digital camera.

My apologies for the error.

Regards,

Dave.

[TIMTAPE]

Originally Posted by reelguy

Sorry Tim, I have never managed to get hold of an A807 Studer .Nor any other Studer model.Only Revox A77s.
But looking at the pic of that head it does look as if it has had a hard life.
Hope you manage to sort it out.

I was under the impression that heads from the A77 Revox could be used on other Studer ?Revox Mcs but I am not really sure.

Regards Peter W....Reelguy

The head I pictured is actually from a B77. I took it to show Dave. Yes it's very worn but the relief slots (gutters as Ted calls them) are still there -just.

This was my first time with an A807. Lovely machine. Very heavy. The heads are certainly physically different from A77/B77/PR99 models but I wouldnt be surprised if they're similar in terms of performance.

A big difference is that most of the alignment parameters are digitally controlled via adjustable buttons from the front panel. Very easy once you get used to it.

Cheers Tim

[Ted Kendall]

There is little to choose in terms of straight performance between Revox and Studer heads, although in general the mountings are not directly compatible. However, I believe there is rather more meat in the gap area on Studer heads. This gives longer life, but requires occasional adjustment as the head inductance changes with wear. On a Studer, of course, this is no problem. Revox machines generally did not have adjustable replay EQ, so the head appears to have been designed with thinner pole pieces to keep the top within fairly fine limits until the head wears out altogether. I've only done this once - one week the head was fine, the next all the top had gone and I could see the gap. Oops...

[TIMTAPE]

Thanks Ted.

Interestingly, when I looked at the heads when they were out, there was still quite a bit of meat there. I dont understand why Studer didnt cut deeper slots in the first place, preferably down to the same level as the where the pole pieces open up. Then you'd only have to relap when needed, until the end of the head's life.

Yes all the Revoxes I've seen have only had repro level.

I think the official recommendation for replacement of Revox heads was after the wear flat equalled or exceeded 2mm or 3mm wide. I saw a number of machines where the flat area was a lot wider than that!

Yes my experience too that when the gap opens up it happens very quickly.

Cheers Tim